Development and validation of an inductively coupled plasma mass spectrometry method with optimized microwave-assisted sample digestion for the determination of platinum at ultratrace levels in plasma and ultrafiltrate plasma

A highly sensitive inductively coupled plasma-mass spectrometry (ICP-MS) method with microwave-assisted sample digestion for the determination of total platinum in rat whole and ultrafiltrate plasma was developed and validated. A first step of this study concerned the optimization of the mineralization procedure, in order to obtain good extraction recovery (higher than 90%) and repeatability (less than 6%) and the absence of matrix effect. ICP-MS analysis was then performed using the “hot plasma/protective ion extraction” mode, achieving high sensitivity and very high signal/noise ratio. Iridium was added as internal standard. The method was then submitted to validation, performed according to the FDA Bioanalytical Validation Methods guidelines and to the Eurachem guide. Validation was carried out in terms of limit of detection (LOD), limit of quantitation (LOQ), linearity, precision, accuracy and stability. An instrumental LOQ of 1.9 ng L-1, corresponding to a concentration of 955 ng L-1 in matrix under the adopted conditions, was obtained, allowing the quantitative analysis of Pt ultratraces. Instrumental linearity was verified in the range 1.9-14000 ng L-1, corresponding to a concentration range from 955 ng L-1 to 6825 μg L-1 in matrix. Accuracy was evaluated by analyzing control samples for both matrices at different concentration levels; a good agreement (<15%) was obtained. Sample stability was tested by analyzing control samples maintained for 4 hours at room temperature or submitted to three freezing-thawing cycles. Finally, the developed method was applied to the analysis of plasma and ultrafiltrate plasma of rats treated with oxaliplatin-base drug, thus demonstrating its reliability in pharmacokinetic studies.